docs: def clip_mean(imt, mean):
      """
      Clip GMPE mean value at 1.5 g for PGA and 3 g for short periods
      (0.02 < T < 0.55)
      """
      if imt.period == 0:
          mean[mean > 0.405] = 0.405
  
      if 0.02 < imt.period < 0.55:
          mean[mean > 1.099] = 1.099
  
      return mean